1. Field of the Invention
The present invention relates to a method of installing fasteners in sandwich-type composite panels and more particularly, a method of integrally welding a fastener insert into a sandwich-type panel.
2. Description of Related Art
Lightweight structural panels are commonly formed of a sandwich of two flat resin facings and an intermediate core structure which are bonded together and are frequently used as flooring, bulkheads, and the like in commercial aircraft. Such sandwich panels possess a desirous characteristic of being lightweight, while still providing relative high strength and stiffness needed for structural support in the aircraft.
Various forms of fasteners have been developed to be secured in a hole that has been cut into the aircraft panel, such as the sandwich panel fastener of U.S. Pat. Nos. 3,510,916 and 4,846,612. Sandwich panels can utilize an exterior sheet or skin, such as a glass fiber reinforced polyetherimide, which is then adhered by an adhesive to a core structure. The core structure can be a plurality of strips of metal foil or other thin lightweight material, which have been bent to form a plurality of honeycomb cells. The opposite side of the core structure is adhered to a similar resin sheet to form a sandwich configuration.
The fastener insert can be installed in a lightweight sandwich panel by first drilling a hole of the desired size for the particular insert. The insert is then inserted within the hole and is usually secured by a potting compound that will harden to provide an anchorage for the insert. Various different methods have been resorted to in an attempt to position the insert into the hole and to hold it in the proper position, while permitting the potting compound to be introduced into the core structure and to set to hold the fastener in its appropriately aligned position. An adhesive cover has been utilized to temporarily attach itself to the periphery of the panel, while holding the insert adjacent the panel surface to receive the potting compound. The adhesive cover is subsequently removed when the insert has been appropriately anchored.
The prior art is still seeking to optimize the manner of installing inserts in a lightweight panel structure and thereby realize a savings in labor cost.